The biological and biochemical functions of DNA and RNA are determined by their structural and dynamic properties in solution. A major contribution to the structural flexibility of nucleic acids is provided by the phosphodiester backbone, but experimental methods have not been developed which will provide a description of this portion of the structure in solution. NMR spectroscopy is the ideal method to determine structural and dynamic properties of molecules in solution, and we propose to use 31P and 17O NMR spectroscopy to study oligonucleotides. The assignment of 31P resonances of oligonucleotides will be accomplished by the chemical synthesis of oligenucleotides which are labelled in a sequence specific manner with 17O in the phosphoryl oxygens of the phosphodiester linkages. 17O is a quadrupolar nuclesus with a nuclear spin equal to 5/2. One consequence of the quadrupolar nature of the nucleus is that the 31P resonances of directly bonded phosphorus nuclei will be significantly broadened, allowing the 31P resonances to be assigned to particular phosphodiester linkages. Since 17O has a nuclear spin, it can be observed by NMR techniques; the quadrupolar nature of the nucleus will allow direct measurement of the flexibility of the phosphodiester bonds, since the linewidths are directly proportional to the motional freedom of the nucleus. Thus, the synthesis and NMR properties of (17O)-labelled oligonucleotides will provide a large amount of previously inaccessible information regarding their structure and dynamics in solution.